1. Field of the Invention
This invention relates to quaternary sulfides and selenides containing barium or strontium and a mixture of transition metals containing a metal of Periodic Group V and a metal of Periodic Groups VI to VIII or Cu. These compounds are useful as semiconductors.
2. Description of the Prior Art
Ternary sulfides are known with the formula MM'S.sub.3 wherein M is an alkaline earth metal of Periodic Group II and M' is a transition metal of Periodic Group IV; e.g., the compounds SrTiS.sub.3, BaTiS.sub.3 and BaZrS.sub.3 are described by Hahn et al., Z. Anorg. Chem., vol. 288, p. 269 (1956); and the compounds BaTiS.sub.3, BaZrS.sub.3 and SrZrS.sub.3 are described by Clearfield in Acta. Cryst., vol. 16, pp. 135-142 (1962). Analogous compounds have been reported with transition metals of Group V; e.g., BaTaS.sub.3 is described by Aslanov et al. in Russ. Jour. Inorg. Chem., vol. 9, p. 1317 (1964); and BaVS.sub.3 and BaTaS.sub.3 are described by Gardener et al. in Acta. Cryst., vol. B25, p. 781 (1969), and in Inorg. Chem., vol. 8, No. 12, pp. 2784-2787 (1969). Their formulation is consistent with the known ability of the Group V transition metals to form not only pentavalent but also tetravalent ions, particularly in combination with a reducing species such as sulfide ion.
Quaternary sulfides have also been reported in the form of solid solutions of ternary compounds of two different tetravalent metals; e.g., BaTi.sub.1.sub.-x V.sub.x S.sub.3 described by Gardener, Ph.D. Thesis, Department of Chemistry, Brown University, Providence, R.I., 1969.